Hyundai Manila Bay service center manager treats customers badly

I would like to share my sister's experience at Hyundai Service Center at Manila Bay which happened last week. My sister recently acquired a brand new car from this branch and returned a few weeks after buying to report that the rear view mirror's camera (it was an i10 gold) should be adjusted properly. A few minutes after entering the service center, the manager was calling out LOUDLY to the owner of a certain car (my sister's), when my sister responded POLITELY, the manager rudely demanded for the car keys. My sister inquired for what reason. Take note that at this point, the "manager" has not yet identified himself and his reason for looking for my sister. The manager then LOUDLY demanded again for the keys, "titignan ko nga!" my sister, still trying to be nice, asked "kayo po ba yung gagawa?" of course my sister won't instantly hand out keys to anyone. The manager suddenly pulled the keys out of my sister's hands, entered the car and started checking the car out. My sister went back to call her friend who was on the other part of the service center and when they came back, my sister's friend asked the manager what was going on. The manager then furiously stepped out of the car and in a loud voice said "dapat kasi iniiwan niyo yung susi dito! yan ang procedure namin dito!" my sister's friend then told him that they weren't informed of this procedure and that there is no reason to shout. at this point, the guys working at the service center huddled around because the loud voice of the manager attracted their attention. The manager looked like he was about to hit my sister when her friend stepped up and said "bumili kami ng kotse dito tapos ganyan niyo kami ta-tratuhin?" the manager dashed out of the service center. My sister and her friend asked for the name of the manager but no one there would like to provide the name. If there's anyone here who can help us in any way, please reply here. Thanks.